Love has always been a mystery to mankind and is a very puzzling feeling. Read this article to learn the science behind the emotion of love.
Introduction
Love has always been a subject for great poets, painters, storytellers, and daily conversation, and as a society we have called it many names—addictive, overwhelming, neurotic, complicated. Jane Austen once wrote, “There is no charm equal to tenderness of heart.” Inside our brains, however, what are the complex, many-layered inner workings of emotion happening beneath the four-letter word that seems to tie us all together? Even though it is a truth universally acknowledged that there is no single ‘formula’ for how love works, we can, however, look at love through a scientific scope, understanding the role each hormone in our body plays.
A major hormone, oxytocin, which acts as a neurotransmitter, is also called the “love hormone.” It is a peptide hormone, which means its molecules are made of short amino acid chains; moreover, it is a neuropeptide produced in the hypothalamus and released by the posterior pituitary into the bloodstream. It is released in substantial amounts during intercourse, breastfeeding, childbirth, or in response to stimuli like touch and warm temperature—all of which act as precursors to bonding. Oxytocin prompts the production of prostaglandins, which increase uterine contractions. In breastfeeding, the hormone helps to move breast milk from the mammary ducts to the nipple, fostering a maternal bond between mother and child. Whilst breastfeeding a newborn, the mechanoreceptors found in the nipple and the cervix are activated, leading to an increase in the release of oxytocin in the brain. The production of oxytocin and its secretion into the bloodstream causes milk to be let down into the breast and helps the baby get the milk easily. This is called the oxytocin reflex, also known as the “letdown reflex” or “milk ejection reflex.” The whole thing operates within a positive feedback loop, meaning that the hormone causes an action which prompts the release of more hormones of the same kind.
Another hormone, phenylethylamine or PEA, is an amphetamine-related chemical that affects people’s moods and energy, which is also labelled as the “chemical of love” or the “love molecule” to name a few. It usually makes people more lively like similar stimulants such as oxytocin. PEA triggers the release of two neurotransmitters: dopamine, which is responsible for the sensation of pleasure, and norepinephrine, which is responsible for physical manifestations like sweat and hyperventilation. Phenylethylamine is present in chocolate, leading many to believe that it is an aphrodisiac. However, blood levels of PEA do not rise after eating chocolate, and the PEA we ingest is metabolized quickly that almost none of it makes it to the brain. Furthermore, the pleasure of eating chocolate has nothing to do with phenylethylamine but can be attributed to the presence of caffeine, anandamide, and theobromine.
According to Dr Helen Fisher (1996), love can be divided into three: lust, attraction, and attachment. All three of these operate with interconnected hormones unique to their function.
Lust
The first category is characterized as sexual desire or gratification, a trait linked to the innate need to reproduce in living organisms. Chemicals like pheromones act as “go signals” and are capable of acting like hormones coming from the secreting individual which affects the behaviour of the receiving individuals. Pheromones are more commonly linked with animals. Its effect on humans is still an ongoing debate as humans do not have a functioning vomeronasal organ and the vomeronasal sensory function is therefore non-operational. It is developed in early fetal life, however, all structures except the vomeronasal duct undergo regression with age.
The hypothalamus controls the production of the two primary hormones in this category: the sex hormones, estrogen and testosterone, produced in the ovaries and testes, respectively. These hormones are commonly labelled as being female and male, however, both play a role in men and women. In fact, testosterone is an androgen, hormone that contributes to reproduction and growth in both sexes. Thus, these hormones work mutually.
Attraction
In attraction, the three major hormones (dopamine, norepinephrine, and serotonin) flow through the body, prompting a surge of positive emotion. This is what that “fuzzy feeling” is made of. Dopamine, which is released in the hypothalamus is a stimulant that fuels ecstatics. Norepinephrine, or noradrenaline, is also related to our fight-or-flight response. A specific combination of these two hormones prompts energetic feelings and the feeling of being giddy, but they can also lead to insomnia and a diminished appetite. Serotonin is linked to social behaviour, memory, appetite, mood, and desire. Interestingly, serotonin is seen to reach lower levels in this phase. When falling in love, cortisol levels rise to deal with the stress and anxiety of romantic attraction, often manifesting physically through sweaty palms and an increased heart rate. As cortisol rises, serotonin levels drop.
Attachment
The last category, attachment, mediate social relationships like friendships, familial bonds, as well as other complex intimacies. Attachment is an essential factor in order to establish long-term relationships, whether romantic or platonic. The primary hormones involved in attachment are vasopressin and oxytocin, which are responsible for the feeling of attachment and care we feel for people close to us. Many believe vasopressin plays a role in social interactions between humans, such as pair bonding. Larry Zweifel, UW Medicine neuroscientist, said, “When we meet someone and we find a connection, there’s an increase in oxytocin.”
Conclusion
To conclude, love is a series of networks working in a bunch of blurry, interconnected pathways, hormones, and chemicals. We have barely scratched love’s inner workings and scientists are still trying to discover the full picture of how love works. It may remain that way for a long time, but what did we expect from such a complex emotion? To quote the 2003 movie "Love, Actually", “Often [love] is not particularly dignified or newsworthy, but it's always there—fathers and sons, mothers and daughters, husbands and wives, boyfriends, girlfriends, old friends.”
No matter how many angles we see love from, it will certainly remain part of human nature that love is all around, working in small fragments like chemicals, creating a community all around the globe.
Bibliography
1. Fisher, H. (1996). Lust, Attraction, and Attachment in Mammalian Reproduction. Human Nature, 9(1), 23–52. http://www.helenfisher.com/downloads/articles/10lustattraction.pdf
2. Infant and Young Child Feeding: Model Chapter for Textbooks for Medical Students and Allied Health Professionals. (2009). World Health Organization. Retrieved 2023, from https://www.ncbi.nlm.nih.gov/books/NBK148970/.
3. Mount Elizabeth Hospital. (2023, March 28). The science behind why we fall in Love: Stages of love. MEH. https://www.mountelizabeth.com.sg/health-plus/article/the-science-behind-why-we-fall-in-love
4. Oxytocin: The love hormone. Harvard Health. (2023, June 13). https://www.health.harvard.edu/mind-and-mood/oxytocin-the-love-hormone
5. Schwarez, J. (2020, February 24). The “Chemical of Love.” Office for Science and Society. https://www.mcgill.ca/oss/article/nutrition/phenylethylamine-chemical-love
6. Talbot , C., & Boynton , E. (2023, February 14). 3 Ways Brain Chemistry influences love and Attraction. Right as Rain . https://rightasrain.uwmedicine.org/life/relationships/brain-chemistry-influences-love
7. Uvnäs-Moberg, K., Handlin, L., & Petersson, M. (2015). Self-soothing behaviors with particular reference to oxytocin release induced by non-noxious sensory stimulation. Frontiers in Psychology, 5. https://doi.org/10.3389/fpsyg.2014.01529
8. What is the science behind Love?. Wonderopolis. (n.d.). https://wonderopolis.org/wonder/what-is-the-science-behind-love
9. Witt, M., & Wozniak, W. (2006). Structure and function of the vomeronasal organ. Taste and Smell, 70–83. https://doi.org/10.1159/000093751
10. Wu, K. (2020, June 19). Love, actually: The science behind lust, attraction, and companionship. Science in the News. https://sitn.hms.harvard.edu/flash/2017/love-actually-science-behind-lust-attraction-companionship/
コメント